London - Serena Williams said Wimbledon fans should be made to explain themselves after 'blacking up' their faces in a bizarre tribute to Australian star Nick Kyrgios.
The controversial and flamboyant Kyrgios's Wimbledon run, which ended in a fourth round defeat against Richard Gasquet on Monday, had inspired the odd trend of people posting pictures on the internet of their faces smeared in Vegemite and Nutella.
Kyrgios, 22, has tweeted his blessing to what some may interpret as a politically incorrect gesture.
But five-time Wimbledon winner Serena was less impressed when told of the incident after her last 16 win over sister Venus.
"Oh, gosh. Really? I didn't know that," Serena said.
"I think you're better asking the fans that question.
"Maybe they can give you some insight. And let me know, I'd be interested to know."